Electric water heater: Any insight/experience?

svsagres

Solar Enthusiast
Joined
Nov 14, 2021
Messages
57
Yeabutt.

Propane is annoying to get refills for if you have enough space and money for batteries.

Personally I'd use a diesel heater with heat exchanger that can double as an engine heater. If it were on an rv rather than a trailer anyways.

Might still consider it for a trailer too.
It wasn't cheap, but a friend of mine has a Kabola boiler on their 46 foot boat. It runs 6 zones of heating on the boat, heats their hot water, and just sips diesel. It's efficient enough that the exhaust pipe can exit the side of the fiberglass hull without much issue (the exhaust gasses are that cool). While underway, though, they just use waste heat from their engine.
 

Honuz

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Oct 22, 2020
Messages
186
I know my coffee maker works and it could be a water heater. In a pinch, I could pour it's content into a basin with cold water for what ever reason. Not as nice as on tap but, for 20 bucks, worth a try.
I'm living in a tent for nearly 2 years ( building my house) and I use cold water, it's even easier...😀
Those days water is at 5°C, and it's not that hard to shower when you are used to it.
Little more complicated to wash hairs though.
Big advantage, I use like 5-10liters to wash myself entirely. I'm using an old tool, a couade
artimage_63466_422794_201004131547143.jpeg
 

DJSmiley

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Aug 13, 2020
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470
I have installed an Elgena KB6 boiler in my van. That has a capacity of 6L (1.6 gallons). Its a rather cheap unit (about 150 GBP / 200 USD).

I don't have a shower, so not much demand for large amounts of hot water. I have the 12V version. It only draws 200W. So yes, it takes a while to heat, but this has the benefit of not being a huge current draw from the batteries. (Altough the total amount of energy required is still the same)

SInce I have a small submersible pump (only use it for the kitchen) I could use this one. Its a plastic one, not suitable for a pressure pump, but for me it's fine. Insulation on the unit is crap. I've added some Armaflex insulation to slightly improve it (and it's installed in a closed space underneath my bench).
Still, it requires a decent battery bank. I think it takes about 35Ah to get water from 10C to 80C), and another 20-25Ah to keep it on temperature (so approx 55-60Ah each day). Since I have a 280Ah LFP and 320W of solar, that generally is not an issue, but if you don't have sufficient battery capacity / solar available things might be different.
 

efficientPV

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Sep 24, 2019
Messages
482
I now use this $150 shipped 50L (13 gallon from China) which needs extra insulation. The ECOsmart 6 gallon is also nice pictured to the left. Both of these ran on only 60V panel power. I used to have a 10 and 6 gallon in series. I even run a dishwasher.
 

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Bossrox

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May 21, 2021
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Location
Columbia, SC
I'm a plumber as well as building my solar system. I can tell you this, everytime you open up the hot water that heater will fire up. It won't stay on very long tho, maybe a couple minute til it's recovered so your frequency of hot water use will determine how much demand your system will provide. Except for you saying you have a 3000 watt inveter, that's plenty to run it off but no mention of your battery bank size. if it's small, that could deplete them pretty fast without active solar.
 

svsagres

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Joined
Nov 14, 2021
Messages
57
I'm a plumber as well as building my solar system. I can tell you this, everytime you open up the hot water that heater will fire up. It won't stay on very long tho, maybe a couple minute til it's recovered so your frequency of hot water use will determine how much demand your system will provide. Except for you saying you have a 3000 watt inveter, that's plenty to run it off but no mention of your battery bank size. if it's small, that could deplete them pretty fast without active solar.
On my boat, I’m looking at putting in a contactor that will only turn on the element when the engine is running or the boat is plugged into shore power.

Eventually we’ll replace the engine with one that has a freshwater coolant loop, and plumb that through the hot water tank. Capture all the waste heat we can!
 

bfitzgerald

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Joined
Nov 25, 2021
Messages
2
I am new to this forum, but not new to solar and off grid living. We have an off-grid cottage in northern Canada and we spend 5 or 6 months there in the summer. A few years ago I upgraded the solar power to get the cottage power system to operate more like on grid than off grid. This means we have the dishwasher, clothes washing machine, 2 large refrigerators, a mid sized deep freeze and electric appliances like coffee makers, kettle, microwave, really everything you would have at home including a couple of big LED TV's and satellite receiver. The exceptions are the kitchen stove/oven and the hot water heater. For hot water I use a 6 gallon RV style propane water heater. This works pretty well. We always have hot water and the little tank recovers very quickly. I have a 3800w solar array and in the summer there is lots of hours of sunshine so I have power to spare. I was looking for a way to use the excess power to heat water but importantly, I needed to protect my batteries and do this more or less automatically. I thought about diverting power from the panels to an electric water heater to preheat water for the propane heater but then I came across a very inexpensive and easy to install solution. It is a solid state relay that will turn on/off a 120 vac outlet based (loosely) on the state of charge of the battery bank. I have a 120 v -10 gallon water heater (1500w) plugged into that outlet. Of course there is a caveat - you need a charge controller or an inverter with an AUX DC power output that is programmable. Many of the inverters and charge controllers have this feature. I use a Schneider CC and inverter - both have programable AUX DC output capability either of which I can program to turn the outlet on/off based on the voltage of the battery bank. The following link is to a product sold by Sparkfun:


Check it out if you have the equipment to use it and don't let the cost discourage you. This set up with a $10 relay provides around half of our hot water each season. Simple to operate and protects the most important part of the power system, the batteries....bank account.

Brian
 

Honuz

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Joined
Oct 22, 2020
Messages
186
I am new to this forum, but not new to solar and off grid living. We have an off-grid cottage in northern Canada and we spend 5 or 6 months there in the summer. A few years ago I upgraded the solar power to get the cottage power system to operate more like on grid than off grid. This means we have the dishwasher, clothes washing machine, 2 large refrigerators, a mid sized deep freeze and electric appliances like coffee makers, kettle, microwave, really everything you would have at home including a couple of big LED TV's and satellite receiver. The exceptions are the kitchen stove/oven and the hot water heater. For hot water I use a 6 gallon RV style propane water heater. This works pretty well. We always have hot water and the little tank recovers very quickly. I have a 3800w solar array and in the summer there is lots of hours of sunshine so I have power to spare. I was looking for a way to use the excess power to heat water but importantly, I needed to protect my batteries and do this more or less automatically. I thought about diverting power from the panels to an electric water heater to preheat water for the propane heater but then I came across a very inexpensive and easy to install solution. It is a solid state relay that will turn on/off a 120 vac outlet based (loosely) on the state of charge of the battery bank. I have a 120 v -10 gallon water heater (1500w) plugged into that outlet. Of course there is a caveat - you need a charge controller or an inverter with an AUX DC power output that is programmable. Many of the inverters and charge controllers have this feature. I use a Schneider CC and inverter - both have programable AUX DC output capability either of which I can program to turn the outlet on/off based on the voltage of the battery bank. The following link is to a product sold by Sparkfun:


Check it out if you have the equipment to use it and don't let the cost discourage you. This set up with a $10 relay provides around half of our hot water each season. Simple to operate and protects the most important part of the power system, the batteries....bank account.

Brian
I'm not sure i understand exactly what you do, but as soon as the heater is switched on and if there is not enough PV power, it will use batteries.... then your switch will turn the heater off till the batterie is full again.
In most inverter you can do that even without an SSR, cause they got a dry contact (we call it like that in my country) that will switch on/off something depending on battery state for example.
But perhaps i missed something ?
 

bfitzgerald

New Member
Joined
Nov 25, 2021
Messages
2
I'll try to describe it a different way. I have the AUX DC programmed to power on the water heater when the batteries are charged to 60v (48v system). The power to the water heater will stay "on" as long as the battery voltage is greater than 52v. If the battery voltage drops to 52v, the power to the water heater is turned "off" and will remain off until the battery reaches 60v (again). This could happen several time a day if it is partly cloudy. My equipment will not turn on an AC source which is why I need the relay.
 

740GLE

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Joined
Apr 30, 2021
Messages
635
So what’s the range of your water tank temperature seen while operating only under PV? Is it an 80 gallon tank?

Are you raising it to 160-180 then down to 110f by the time you hit morning?
 

efficientPV

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Joined
Sep 24, 2019
Messages
482
Far more efficient and cheaper. This is a module I sent to New Mexico end of summer. Two wires in, two out and it doesn't heat up like the techluck. I was in contact with someone the other day who had a video praising the techluck. He now says he scrapped the techluck as it became unreliable over time. Likely due to the tiny capacitors that were used.
 
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OM617YOTA

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Joined
May 27, 2021
Messages
119
I have the exact water heater listed in the OP, for immediate hot water at my bathroom sink, which is far from the house water heater.

Even if you go electric after all, don't go with that one; it's garbage. Doesn't maintain temperature at all, has burns through thermostats, and now the tank is rusting from the inside. Badly. I need to replace it before it pops and floods my house.
 
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